The present invention relates to passive infrared motion detectors of the type used in residential outdoor lighting fixtures. The lighting fixtures may, for example, illuminate a walkway or driveway when a person or automobile approaches. The invention is more particularly directed to arrangements for limiting the detection angle of the motion detectors.
Lighting fixtures that automatically turn on a light when a person or a motor vehicle approaches have been known for some time. A popular form of such a lighting fixture includes a device that is responsive to infrared radiation emitted by a person or motor vehicle as the person or vehicle moves within the field of view of the device. These devices are generally referred to as passive infrared, or “PIR,” motion detectors. These detectors are incorporated into the lighting fixture housing to trigger the lamp upon detection of the person, motor vehicle, or like heat emitting object.
PIR motion detectors in the prior art typically have a fixed field of view. However, the fixed field of view may be too wide or too narrow to fully meet a particular user's needs. For example, when an outdoor light with a motion detector is affixed to an exterior wall of a house, the motion detector may detect motion both within the user's own yard and also motion that occurs in a next door neighbor's yard. The user is not able to adjust the detection angle to exclude motion in the neighbor's yard from detection. There have been attempts at addressing the field of view of the motion detector.
For example, U.S. Pat. No. 5,442,532, issued Aug. 15, 1995, to Boulos et al., discloses an arrangement for adjusting the field of range of a motion detector that is built into the housing of a decorative lamp. In particular, a hexagonal fixture is turnable about a vertical axis to pivot the infrared detector and the associated motion detection circuitry. In this way, the user can modify the field of range by rotating the motion detector. This arrangement does not, however, allow the user to change the detection angle. Rather, it simply allows the user to shift the field of range to a different area.
U.S. Pat. No. 5,626,417, issued May 6, 1997, to McCavit, is directed to a decorative lamp with a motion sensor incorporated into the base of the housing. The base that contains the motion sensor may be rotated along a vertical axis relative to the rest of the housing to change the field of view of the motion sensor.
Others have used mirrored optics, lenses, or the like to control the field of view of the motion detector. Examples of such devices include U.S. Pat. No. 6,348,691 to Sandell et al.; U.S. Pat. No. 6,346,705 to Lee et al.; and U.S. Pat. No. 3,958,118 to Schwarz.
It is also known in the art to snap one or more plastic covers onto the outside of the housing to limit the detection angle of the motion sensor. Another known approach is to glue a piece of tape across a portion of the aperture through which signals pass, thereby limiting the angle of detection. However, both approaches are unsightly, somewhat cumbersome to implement, and cannot withstand the effects of weather if the lamp and detector are used outdoors.